#include "apue.h"
#include <pthread.h>
#include <stdio.h>

struct foo
{
    int f_count;
    pthread_mutex_t f_lock;
    int f_id;
};

struct foo* foo_alloc(int id)
{
    struct foo* fp;
    if ((fp = (struct foo*)malloc(sizeof(struct foo))) != NULL)
    {
        fp->f_count = 1;
        fp->f_id = id;
        if (pthread_mutex_init(&fp->f_lock, NULL) != 0)
        {
            free(fp);
            return (NULL);
        }
    }
    return (fp);
}

void foo_hold(struct foo* fp)
{
    pthread_mutex_lock(&fp->f_lock);
    fp->f_count++;
    pthread_mutex_unlock(&fp->f_lock);
}

void foo_rele(struct foo* fp)
{
    pthread_mutex_lock(&fp->f_lock);
    if (--fp->f_count == 0)
    {
        pthread_mutex_unlock(&fp->f_lock);
        pthread_mutex_destroy(&fp->f_lock);
        free(fp);
    }
    else
    {
        pthread_mutex_unlock(&fp->f_lock);
    }
}
